Nickel and cobalt recovery from ammoniacal solutions



NICKEL AND COBALT RECOVERY FROM AMMONIACAL SOLUTIONS Conrad B. Bare,Lebanon, and Robert L. Clauser, Schaef- 'ferstown, Pa., assignors toBethlehem Steel Company, a corporation of Pennsylvania No Drawing.Application October 12, 1956 Serial No. 615,710

10 Claims. c1. 23-183 This application is a continuation-in-part ofapplication Serial No. 358,908, filed June 1, 1953, now abandoned.

This invention relates to a process of separating nickel from cobaltfrom solutions containing appreciable concentrations of each metal, andmore particularly to the selective precipitation of nickel,substantially free of cobalt, from ammoniacal solutions obtained fromtreating nickeliferous lateritic ores.

In previous practice, it is known that a degree of separation of nickelfrom cobalt has been obtained by the fractional distillation of ammoniaand carbon dioxide from ammoniacal ammonium carbonate solutions, inwhich part of the metal content is precipitated at an improved nickel tocobalt ratio.

We have found that when an oxidized ammoniacal ammonium carbonatesolution, obtained from leaching an ore and containing nickel andcobalt, wherein the cobalt is present in the cobaltic state, is treatedwith an alkali metal or alkaline earth metal hydroxide under controlledtemperature conditions, nickel can be precipitated substantially free ofcobalt. Furthermore, the cobalt remaining in solution, after removal ofthe nickel therefrom, can be recovered from solution by well-known meansand in a state comparatively free of nickel.

One example of efiecting the separation of nickel from cobalt, inaccordance with our invention, is given below:

EXAMPLE I Ni 8.4 Go. 1.1 NH 125 C 110 To 7.5 liters of this solution wasadded 1710 grams of sodium hydroxide in the form of a solution. The

reacting mixturewas maintained at a temperature of approximately 100 F.A light green nickel hydroxide? precipitate formed and this precipitatewas separated from the solution by filtration and thoroughly washed. Theprecipitate contained 99% of the nickel and only 3.6% of the cobaltpresent in the original solution. The remaining solution was heated toprecipitate the cobalt. From.the results it will be seen thatsubstantially all of the nickel was precipitated at a nickel to cobaltratio of 210 to- 1 from a solution containing a nickel to cobalt ratioof less than 8 to 1.

A modification of the process described in the fore:

' going example is shown in the following:

the cobalt. After this treatment, the solution analyzed as follows:G./l.'

Ni 7,0 Co 0.89 NH 20.6 CO 13.6'

EXAMPLE II The pregnant leach liquor used in Example I was steamdistilled to drive oil, a large fraction of excess ammonia and carbondioxide. In this instance the distillation was discontinued at the pointwhere a precipitate just begins to form. The solution was cooled,filtered to remove any iron and manganese precipitate, and aerated tooxidize To 9 liters of this solution was added 228 grams of sodiumhydroxide in the form of a 10% solution. Thetemperature of the reactingmixture was maintained at approximately F. A nickel-containingprecipitate was formed, the precipitate being separated from solu-' tionby filtration and washed. The precipitate contained 99.8% of the nickelbut only 4.5% of the cobalt originally present in the partiallydistilled solution. Thus, substantially all of the nickel wasprecipitated at a ratio of EXAMPLE III Ni 9.1 Co 1.0 NH 20.0 CO 14.8

was added 103 pounds of sodium hydroxide as a 10% solution. The reactingmixture was maintained at 100 F. The precipitation of the nickel wascarried out continuously at a solution rate of 4.2 gal./min. Afterseparating the precipitate from the solution by filtration andthoroughly washing it with water, the precipitate analysis indicated anickel to cobalt ratio of 94 to l. The precipitate contained 99.9% ofthe nickel but only 9.7% of the cobalt originally stripped solution.

Impurities such as iron or manganese, if present in:

solution, precipitate when ammonia and carbon dioxide are driven oltfrom solution to about the point where nickel begins to precipitate.Precipitates of these impurities carry with them small amounts of nickeland. In practice we prefer to remove such precipi cobalt. tatedimpurities by filtration before the addition of so-. dium hydroxide,thus preventing the contamination of the nickel precipitate with iron,manganese and cobalt.

When most of the ammonia and carbon dioxide are driven off fromsolution, as by steam distilling in, Examples II and III, considerablyless alkali is required to precipitate the nickel.

In Examples II and III, the

Patented Mar. 24, 1959 To 365 gallons of this partially:

present in the partially.

I ammonical ammonium carbonate solution of nickel and cobalt was steamdistilled to the point where the nickel just began top'recipitate,

cooled, filtered, and sodium hydroxide added. While a thepmcess" can beefieticeiy earrteu"cushy watching for the first appearance of nickelprecipitate, we have found it advantageous, in practice, to stop theboiling when the ammonia eoncentrationof the solution reaches a valueapproximatiiigthe'ammonia concentration at the time of incipient nickelprecipitation. Each ammoniacal ammonium carbonate solution of nickelandcobalt has a panama: ammonia concentration at the time of -incipieritprecipitation of'nickel, i. e-., the point at which nickel justbegins'to precipitate. This is not a constant value, but one whichvaries with the concentration of nickel and 'cobalt in the solution. Todetermine the point of incipient precipitation of nickel for anyparticunrsbluadmo betr'eated, we'takea small sample of the solution andsteam distill until the nickel just begins to precipitate, cool thesolution, and determine the approximate ammonia concentration bytitrating with l N I ICl', using methyl'orange indicator. This titrationgives bfu' 'aa approximate indication of the ammonia concentration, asmetal values in the solution will react with hydrochloric acid beforethe end point is reached. However, we have found that'this titration hasproved satisfactory as a control measure. Having thus ascertained theapproximate concentration of ammonia at 'the time of incipientprecipitation ofnickel, the solution,-to be' treated by our process, issteam distilled to remove ammonia and carbon dioxide'until the ammoniaconcentration is found to approximate that previously found by test tocorrespond to the'co'ncentration at'thetim'e of incipient precipitationof nickel.- When this concentration is reached, the solution iscooled-to the desired degree, filtered, and sodium hydroxide added.

It is to be noted that the distillation is terminated when the ammoniaconcentration is approximately that previously determined to correspondto that of incipient precipitation of nickel. Exactness is notnecessary. For example, the distillation-may be terminated when thesolution still contains an ammonia concentration somewhat inexcess ofthat previously determined to be that of incipient precipitation ofnickel. Likewise, the distillation'may be terminated'somewhat after theammonia concentration of incipient precipitation of nickel has beenreached.

The amount of sodium hydroxide to be added to precipitate the nickel,varies with difierent solutions. We

have found that a satisfactroy amount to use is that which is slightlyin excess of the stoichiometric equivalent of the carbon dioxidecontained in the particular solution being treated.

f When we refer herein to the ammonia concentration of the solution, orto the amount of ammonia in the solutiomwe mean all of theammoniapresent, whether present as the hydroxide, carbonate or in anyother form; v

'fIn the examples given above, the solution treated conprecipitate isvery low as compared with that of the nickel, and the nickel content ofthe cobalt precipitate is very low as compared with that of the cobalt.If the amount of cobalt relative to the amount of nickel, in a solutionto be treated, 'is greater, or, in other words,

if the nickel to cobalt ratio is less, a higher percentage of'cobaltwillbepresent in the nickel precipitate. The cobaltprecipitate, however,will continue to be very low in nickel". When the solution to be treated"containssuch a nickel to cobalt ratio as to give a nickel 'precipitiatehaving a' cobalt content higher than desired, a the nickelprecipiuitecan be dissolved in an ammoniacal ammonium carbonate solutionand the resulting'solu'tion si bjected to 'the samef treatment as thatgiven to "the selmrbnfaamety; fb'oilin'g tofredu'ce 1 the 4 monia andcarbon dioxide concentration of the solution to-- that which'approximates thatof inc-ipientmrecipitm tion of nickel, cooling,andadding sodium hydroxide to precipitate the nickel. This new nickelprecipitate, thus obtained, will obviously be substantially lower incobalt content than the previous precipitate.

The importance of temperature in the application of our invention isshown by results of tests. described below.

The solution used in Example I was steam distilled as inExample II and,after cooling, filtering andcaerating, three equal 8.7 liter batches ofsolution'were treated with 207 grams of sodium hydroxide as a 10%solution at three difierent temperatures. 'I he resultsare' given in thefollowing table:

7 Table I Nickel Preclpitate, N 1/00 Ratio In each of the three testsindicated in this table, more than 99.5% of the nickel was precipitated.However, due to the instability of the cobaltic amine toward thealkalineagent at higher temperatures, greater amounts of cobalt werecoprecipitated with the nickel, rendering the separation inadequatelyeifective at temperatures above. approximately 125 F. On the other hand,effective separations can be obtained with temperatlllffis as low as 50F. In regard 'to the aeration of the solution prior to the precipitationof the nickel, it may be that the particular solution to be treated issufliciently oxidized as to require no further oxidation. In general weprefer, ,as a precautionary measure to allow the solution to be agitatedfor several hours in the presence of air-before precipitating thenickel. In some instances it was found to be beneficial to extend theperiod of aeration to from 18 to 24 hours. However, we have found thatin treating solutions containing nickel and cobalt values extracted fromlateritic' ores, which solutions were recovered through counter-currentdecantation on a small pilot plant scale, a period of from three tofourhours agitation in an air atmosphere is perfectly satisfactory.

It is advisable, when filtering the solution fromthe nickel precipitate,to do so within a reasonably short time, say within about one hour,after formingthe precipitate. If the nickel precipitate is allowed toremain with the solution for long periods, for example, over night, acertain amount of cobalt will be carried down by the nickel precipitate,thus rendering-alerts efiicient separation thancan be attained when-thefiltration operation is performed more promptly.

Usually we employ sodium hydroxide as the nickel precipitant, but otheralkali metal, or alkaline earth metal, hydroxides such as potassium,calcium and barium may be used. a 1

A modification of our process will now be described, relating to thetreatment of nickel and cobalt solutions which contain such proportionsof cobalt as to give nickel precipitates having a higher cobalt contentthan desired.

In this modification of our process, the ammoniacal ammonium carbonatesolution of nickel and cobaltv to be treated is boiled to lower theammonia and carbon dioxide concentration of the solution to the point ofapproximate incipient precipitation of nickel, and the solution cooled.

Sodium hydroxide is added in an amount necessary, to

rated, and sodium hydroxide added to the solution -in amount suflicientto precipitate the remainder of the nickel and some cobalt. Thisprecipitate is separated from the solution and dissolved in anammoniacal ammonium carbonate solution which is then subjected to thesame treatment given to the original solution in the specific example ofour process first given above.

We claim:

1. A process of separating nickel and cobalt which comprises treating anoxidized ammoniacal ammonium carbonate solution which contains nickeland cobalt values in solution, with an hydroxide of at least one of thegroup consisting of sodium, potassium, calcium and barium at atemperature of not more than 125 F. and thereby precipitating a compoundof nickel, separating precipitated nickel from solution, then heatingthe remaining solution to drive oif ammonia and thereby precipitating acompound of cobalt.

2. A process of separating nickel and cobalt which comprises the stepsof heating an oxidized ammoniacal ammonium carbonate solution of nickeland cobalt compounds to drive oif ammonia and carbon dioxide until theammonia concentration of the solution is approximately that of incipientprecipitation of nickel, cooling the solution below 125 F., adding anhydroxide of at least one of the group consisting of sodium, potassium,calcium and barium to the solution and thereby precipitating a compoundof nickel, separating the precipitated nickel compound from solution andheating the solution to drive oil. ammonia and thereby precipitating acompound of cobalt.

3. A process of separating nickel and cobalt which comprises the stepsof heating an oxidized ammoniacal ammonium carbonate solution of nickeland cobalt compounds to drive off ammonia and carbon dioxide until theammonia concentration of the solution is approximately that of incipientprecipitation of nickel, cooling the solution below 125 F., adding anhydroxide of at least one of the group consisting of sodium, potassium,calcium and barium to the solution and thereby precipitatingsubstantially all of the nickel, separating the precipitated nickelcompound from solution and heating the solution to drive oft ammonia andthereby precipitating a compound of cobalt.

4. A process of separating nickel and cobalt which comprises the stepsof heating an oxidized ammoniacal ammonium carbonate solution of nickeland cobalt compounds to drive oft ammonia and carbon dioxide until theammonia concentration of the solution is approximately that of incipientprecipitation of nickel, cooling the solution below 125 F., addingsodium hydroxide to the solution and thereby precipitating a compound ofnickel, separating the precipitated nickel compound from solution andheating the solution to drive off ammonia and thereby precipitating acompound of cobalt.

5. A process of separating nickel and cobalt which comprises the stepsof heating an oxidized ammoniacal ammonium carbonate solution of nickeland cobalt compounds to drive off ammonia and carbon dioxide until theammonia concentration of the solution is approximately that of incipientprecipitation of nickel, cooling the solution below 125 F., addingpotassium hydroxide to the solution and thereby precipitating a compoundof nickel, separating the precipitated nickel compound from solution andheating the solution to drive otl ammonia and thereby precipitating acompound oi cobalt.

6. A process of separating nickel and cobalt which comprises the stepsof heating an oxidized ammoniacal ammonium carbonate solution of nickeland cobalt compounds to drive ofi ammonia and carbon dioxide until theammonia concentration of the solution is approximately that of incipientprecipitation of nickel, cooling the solution below F., adding calciumhydroxide to the solution and thereby precipitating a compound ofnickel, separating the precipitated nickel compound from solution andheating the solution to drive oif ammonia and thereby precipitating acompound of cobalt.

7'. A process of separating nickel and cobalt which comprises the stepsof heating an oxidized ammoniacal ammonium carbonate solution of nickeland cobalt compounds to drive off ammonia and carbon dioxide until theammonia concentration of the solution is approximately that of incipientprecipitation of nickel, cooling the solution below 125 F., addingbarium hydroxide to the solution and thereby precipitating a compound ofnickel, separating the precipitated nickel compound from solution andheating the solution to drive off ammonia and thereby precipitating acompound of cobalt.

8. In the separation of nickel from cobalt in a solution obtained fromleaching a nickeliferous lateritic ore the process which comprisesoxidizing an ammoniacal ammonium carbonate leach solution of nickel andcobalt compounds, heating the solution to drive ofi ammonia and carbondioxide until the ammonia concentration of the solution is approximatelythat of incipient precipitation of nickel, filtering the solution,cooling the solution below 125 F., adding sodium hydroxide to thesolution and thereby precipitating a compound of nickel, separating theprecipitated nickel compound from solution and heating the solution todrive off ammonia and thereby precipitating a compound of cobalt.

9. A process of separating nickel and cobalt which comprises treating anammoniacal ammonium carbonate solution, which contains nickel andcobaltic cobalt values in solution, with an hydroxide of at least one ofthe group consisting of sodium, potassium, calcium and barium at atemperature not in excess of 125 F. and thereby precipitatingsubstantially all of the nickel, separating precipitated nickel fromsolution, then heating the remaining solution to drive off ammonia andthereby precipitating a compound of cobalt.

10. A process of separating nickel from cobalt which comprises treatingan oxidized ammoniacal ammonium carbonate solution, which containsnickel and trivalent cobalt values in solution, with sodium hydroxide ata temperature of not more than 125 F. and thereby precipitatingsubstantially all of the nickel, separating precipitated nickel from thesolution, then heating the remaining solution to drive off ammonia andthereby precipitating substantially all of thecobalt.

References Cited in the file of this patent UNITED STATES PATENTS1,487,145 Caron Mar. 18, 1924 2,531,336 Hills et al Nov. 21, 19502,711,956 Schaufeberger June 28, 1955 2,735,760 Allen et al Feb. 21,1956 FOREIGN PATENTS 492,158 Canada Apr. 21, 1953

1. A PROCESS OF SEPARATING NICKEL AND COBALT WHICH COMPRISES TREATING ANOXIDIZED AMMONIACAL AMMONIUM CARBONATE SOLUTION WHICH CONTAINS NICKELAND COBALT VALUES IN SOLUTION, WITH AN HYDROXIDE OF AT LEAST ONE OF THEGROUP CONSISTING OF SODIUM, POTASSIUM, CALCIUM AND BARIUM AT ATEMPERATURE OF NOT MORE THAN 125*F. AND THEREBY PRECIPITATING A COMPOUNDOF NICKEL, SEPARATING PRECIPITATED NICKEL FROM SOLUTION, THEN HEATINGTHE REMAINING SOLUTION TO DRIVE OFF AMMONIA AND THEREBY PRECIPITATING ACOMPOUND OF COBALT.